What causes abnormal noise in the eccentric shaft of BMW N46?
2 Answers
BMW N46 reports abnormal noise in the eccentric shaft for the following reasons: Excessive clearance between piston and cylinder wall: Piston pin installed too tightly or connecting rod bearing installed too tightly; Excessive clearance between tappet and its guide hole; Wear of the cam profile; Sometimes, the starting claw is loose, causing the pulley to make noise (especially noticeable when the speed changes). Disordered noise at a certain speed: Camshaft timing gear cracked or its fixing nut loose; Crankshaft broken; Piston pin bushing loose; Excessive axial clearance of the camshaft or its bushing loose. Abnormal noise during acceleration: Connecting rod bearing loose, bearing shell melted or mismatched in size; Crankshaft bearing loose or bearing shell melted; Piston pin broken; Crankshaft broken.
My BMW N46 also had eccentric shaft noise issues before, and the sound was really annoying. I initially thought it was normal noise, but later discovered it was a serious problem. Generally, the causes of such noise are mainly wear or damage to the eccentric shaft components, such as aging and loosening of the bearings inside, or issues with the VANOS system adjustment device. This system is responsible for adjusting the valve timing, and once there's insufficient lubrication or lack of oil, it starts making rattling noises. Additionally, oil pump failure leading to unstable oil pressure is a common factor, and clogged oil pipes can also accelerate wear. Personally, I recommend first checking the oil level and quality—avoid using low-quality oil and ensure timely oil changes and maintenance. If the noise persists, promptly visit a professional repair shop to diagnose it with a scanner. Don’t delay until the engine is ruined; repairs can be costly. When driving, pay attention to gentle acceleration and avoid stomping on the throttle, which can help prevent such issues.
